Ok so recently I went over and fixed the ac system on my 1985 300sd.
What I did
New compressor
New dryer
New expansion valve
Flushed everything very well
Cleaned the condenser
Cleaned the evaporator
Filled with appropriate amount of mineral oil
Pulled 29in HG for an hour and made sure it wasn't leaking
Filled with 2.9 pounds of r12
Replaced all the vacuum pods


Now my pressures look normal
70 degrees ambient temperature
40 and 175psi idle
25-30 and 225 2000rpm

Under 60f my vent temps are perfect, low 40s at idle.

My vent temps, with ambients of 75f+, are around 60f at idle and mid 50s driving around. I clamped off the heater core lines and it didn't make a noticeable difference.

At this point my knowledge has run out of what I should do. After some searching I see people mentioned parallel flow condenser but I figured with r12 my vent temps should be lower. Any feedback would be appreciated.

Are your vacuum pods working? If you have air leaking on the windshield and/or the recycle door not opening, expect poor numbers. Old connectors will keep the system from operating properly, even with new pods.

Aux fan operating?

Tint?

What is the appropriate amount of mineral oil to you?

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

OP:
Re: your quote - "it's barley cold"

barley is a poor refrigerant; try oats

I do have a little air leaking onto the windshield but not much at all. The recirculation door is opening perfectly.

The aux fan is working fine

No tint

I believe i put 5.7 ozs of mineral oil after the flush

I have no idea where you are located, but tint makes a HUGE difference in the system's ability to draw heat from the cabin. Otherwise you are pretty much driving in a microwave, even a new 2017 vehicle cannot cool the cabin. Those temps may be about all you can do with no tint and unknown location...humidity issues? Were your temps listed with the blower on high or low?

Figure out the air leakage, every little bit adds up.

My 300SEL has a dirty evap I believe, takes a while to pull down on the interior with a 100% working system on R12. But hey, I expect nothing less on a car with 317k and no cabin filters to prevent the evap from plugging.

If you park in the sun, place those reflective things you see for about $10 in the windshield AND rear deck area. Yes, seems silly to do both but you can reflect it out.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Fold a bath towel lengthwise and lay it over the defrost. That will direct all the AC to the center and side vents. Will help to identify the problem.

I live in North Carolina so humidity is definitely up there. The temps were with the blower on high. I'll probably invest in a sun shade especially to keep the dash cooler because I realized when I park in my garage and the car is cool it gives it that boost it needs to keep the car cool. I'll look at pricing out tint soon thanks for the suggestion.

Hmm....sounds like you may need a look at the condenser. Is your aux. fan kicking on? Did you clean between the condenser and radiator?

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Sam

84 300SD 350K+ miles ( Blue Belle )

Temps with the blower on high are going to hover in the 50s or high 40s at best. That's all you can expect the system to do. Once it pulls the car down to temp, the vent temp will drop into the mid-low 40s and stay there. At idle, the temp will rise into the low-mid 50s. If your car is doing that, it's working as designed. It takes a while to pull down the cabin temp so the vent temp can drop. At 55˚, the air coming out of the vent should feel "cold" to your hand.

Once the temperature stabilizes in the cabin and the fan speed ramps down, the vent temps will stay in the 40s. You can forget about those kinds of temps until the cabin pulls down though, so be patient and let the system do its job!

You can help improve the operation of the system by giving the condenser a good cleaning. Go to your favorite hardware store and pick up a can or two of foaming coil cleaner (you'll find it with the furnace filters). Spray it on, let it foam up and do it's thing, then hose out with a spray nozzle on the water hose. Repeat and wash out well. You may be surprised what comes out of your otherwise "clean" condenser!

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

Insure the "outside air" vent is shutting. I recently went thru the climate system in my 1985 300D. If similar to your 300SD, one of the vacuum solenoids (behind push-button switch box) controls that (termed "codes"). You can download schematics here. As I recall, the no-vacuum state yields "no outside air", so if you unplug that solenoid, you will get more cooling. If you remove the glovebox liner, you will see the vac actuator and arm to know the door position. The TemperatureReglar boxes tend to get flaky as they age.

I recall if you unbolt the cabin blower, you can access the evaporator upstream-side to get a shop vac hose in to clean out junk. Use a USB endoscope (cheap ebay) to view the condenser fins. Could be crudded up. But, as stated, even when new these AC systems weren't as cold as most U.S. cars. Mine will eventually cool the car, but just barely on our hot days (expected 106 F today), so everyone tries to park in the shade. I tinted the windows in my 1985 300D, which helps a lot. My Chrysler minivans get cooler much faster, but one has rear AC which is almost cheating. But, when driving into the afternoon sun one feels hot even if the cabin air is 60 F, since the sun is evil here.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

This product looks interesting......25 degree lower temps is nothing to sneeze at!

https://www.heatshieldstore.com/

If the condenser does need to be replaced, take a look at the link below to our site's DIY tech article on the procedure. Please let us know if you have any questions!

Mercedes-Benz W126 A/C Condensor Replacement | 1981-1991 S-Class | Pelican Parts DIY Maintenance Article

I have heard those fuzzy dash pads help too. Just ordered one to try. My only vehicle with one is an old BMW (!) that is garaged.

Do you have one of those custom fit windshield reflectors? How long does it last?

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

I like Eclipse sunshades: https://eclipsesunshades.net/ I think AutoZone sells them, too. There is no way I could deal with setting up a sun shade every time I park.





Also apparently parallel-flow condensers and dual fans are stock on 1991 W126s, but I'm not sure if they will fit first generations.

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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

Can't you buy a windshield reflector at Dollar Tree for $1?